Bohemia Interactive makes the military simulations Operation Flashpoint: Cold War Crisis, ArmA and ArmA 2, as well as their expansion packs. They also are behind the upcoming ArmA 3.

All of those games strive for realism and accurate depictions of military combat. They feature open-ended singleplayer scenarios, co-op, and multiplayer. All the games come with a full arsenal of small arms, vehicles, and crew-served weapons for their respective factions. BI games are also notable for their extensive modding support, which supports total conversion mods and easy, modular, content expansion.
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[h2]But I want to play with Facepunch![/h2]
The Facepunch group mainly plays ArmA 2: OA at the moment, the Combined Ops version (both ArmA 2 and ArmA 2:OA). They play custom co-op missions/scenarios most of the time.

Arma 2's (Regular Arma 2, mind you) public community, in my eyes at least, has gone down the drain.

Since Arma 2: Free released, people who play to cause grief have arrived. Before the free version, it was near impossible to find someone griefing on a regular basis. Now, I tried it recently, and at night, public servers go to hell from all of the griefing that goes on. Sometimes there are guys that gun your planes down from the missile Humvee, and others the griefer is in a plane/attack chopper not letting anyone leave the spawnpoint.

Arma 2's (Regular Arma 2, mind you) public community, in my eyes at least, has gone down the drain.

Since Arma 2: Free released, people who play to cause grief have arrived. Before the free version, it was near impossible to find someone griefing on a regular basis. Now, I tried it recently, and at night, public servers go to hell from all of the griefing that goes on. Sometimes there are guys that gun your planes down from the missile Humvee, and others the griefer is in a plane/attack chopper not letting anyone leave the spawnpoint.

I think that most serious players have migrated to OA or ACE, because ArmA 2: Free doesn't support mods.

Regardless, ArmA 2 is not a game I would play on public servers in anyways.

yeah, ACE makes it impossible to rambo shit up with a PKM with 3 boxes of MG ammo and still carry a RPG with 3 rockets, and a pistol with 8 magazines.

Realism.

Uh, yeah. The only hard part would be finding space for 3 LMG box pouches. Just your ability to run long distances is impeded. Arma 3 will have a vest carry capacity system apparently (or was it speculation?) so we can only hope for a JA2-esque system. That way you'll be able to justify the carrying of all that shit, so long as the soldier you play as can lug it around.

Uh, yeah. The only hard part would be finding space for 3 LMG box pouches. Just your ability to run long distances is impeded. Arma 3 will have a vest carry capacity system apparently (or was it speculation?) so we can only hope for a JA2-esque system. That way you'll be able to justify the carrying of all that shit, so long as the soldier you play as can lug it around.

err the weight itself would be pretty damn heavy, that's why.

if they have a vest carry I hope different loadouts show up on your playermodel, that would be nice.

A nice part about CoD4 and CS:S is that the gear you carry shows up on your playermodel.

I remember a two man coop mission a friend of mine made that we played.
Basically, it goes like this:

Nighttime insertion behind enemy lines, with you two (plus an optional squad) assaulting a lightly defended town. This town has slightly good guns/ammo, but most importantly, cars, which will take you to your next objective.
On your way to wherever, you have an option: assault a slightly better defended enemy town (which has APCs or better armored cars, your choice), or skip on the vehicles and assault a helicopter base with what you have.
The helicopter base should be moderately defended, etc etc, fight fight gun shoot boom okay. You get the helicopters, and fly to an airfield, which is well defended. You steal some jets, and complete a bombing run on [INSERT HEAVILY DEFENDED/PLOT IMPORTANT TARGET HERE].

Basically, it's an awesome sabotage mission.

Edited:

Another mission that I made had one person being a criminal, and having to pick up a package and drop it off at a dropoff point, while the other player is a cop, and must kill the other player before they make the dropoff.
This is best done on Zargabad, or confined in another large-ish city. It's also a good idea to have ambient civilians/vehicles on, so the runner can blend in better.

Ah, I find it funny that these threads always seem to pop up when I start playing a game again. I recently got back into Arma 2 (with Ace) and I discovered this thread. The game is so immensely immersive and it's awesomus maximus.